Category Archives: Behaviour

Deep-sea giant squid (Architeuthis) remain one of the ocean’s most charismatic zoological mysteries. While there are plenty of specimens in museums around the world, little is known about their behaviour. Only recently have fleeting glimpses been captured of these creatures in their natural habitat; a 2005 paper (http://rspb.royalsocietypublishing.org/content/272/1581/2583.full) in Proceedings of the Royal Society B described the first ever wild observations of a live giant squid. The author’s photographs showed a huge squid actively hunting at 900m below the surface and they even managed to recover a tentacle that snagged on the bait line (see panels ‘e’ and ‘f’ in the figure).

We also know about the predator-prey interaction between sperm whales and giant squid from the sharp-sucker scars often seen on whale skin and stomach contents (squid beaks are indigestible making them a useful clue to the diet of sperm whales).

Earlier this year, footage taken by a manned submersible was broadcast showing a giant squid 1000m deep in the North Pacific. The footage was captured using near-infrared light (using invisible to humans and squid) since giant squid avoid the bright white light used in conventional filming- perhaps something to do with those enormous eyes? (have a look here: http://www.eeb.yale.edu/ugrad/eeb171pdfs/sa-246-1982.pdf)

See clips from the video at http://www.youtube.com/watch?v=1KN5N1QDaRQ

(picture credit: NHK/NEP/Discovery Channel via Reuters)

As an aside, it’s worth taking a look at this report on the unusual mating behaviour of giant squid – it turns out that male squid giant inject spermatophores directly into wounds that they form on the tentacles of a female:

More recently a somewhat alarming article showed how male squid overcome the challenges of mating at great depths using a ‘super squid sex organ’ – see the long white tubular structure in the picture below.

Predation has shaped the whole of the living world, as prey respond to evolutionary changes in predators, and vice versa. The earlier prey can detect a predator, the greater their possibility of surviving, either by fleeing or hiding. In many aquatic species, prey detection can occur from beyond the grave – for example, Daphnia (“water-fleas”) develop hard protective structures (“inducible defences” – see picture below) when in the presence of water that had contained fish that had eaten Daphnia. The predators have been chemically “labelled” by their prey, enabling other Daphnia to protect themselves.

Daphnia lumholtzi – on the left, reared in the presence of fish, on the right, in the absence of fish

A study about to be published in Behavioural Ecology and Sociobiology shows that these kind of effects can also involve prey learning, even before they have hatched out of the egg. Maud Ferrari and Douglas Chivers investigated the behaviour of woodfrog (Rana sylvatica) tadpoles in response to a predator, the Tiger salamander. These tadpoles show no innate prey recognition, but if they are exposed to the smell of salamander before they hatch from they egg, they avoid predators when they have turned into tadpoles, by reducing their movement. [It may seem counter-intuitive to talk of “smell” in water, but many aquatic animals (including fish) have clearly distinct smell and taste pathways. I’ll blog about this in the future.]

Ferrari and Chivers have taken this a step further, by seeing whether the tadpole embryos can actually learn the threat posed by a predator. To test this, they presented frogspawn with salamander odour coupled with cues from injured tadpoles, for two hours a day over five days, then tested the tadpoles for their responses to the predator.

They found that the amount of freezing shown by tadpoles was dependent on the concentration of the injured tadpole cues coupled with salamander smell, demonstrating that the embryos had learned to associate the two signals. There also seemed to be a time of day effect – the effect was stronger when learning took place in the afternoon, compared to the morning or early evening – although further experiments need to be done to confirm this.

In some species (especially insects), early experience can lead to the non-genetic transmission of preferences from one generation to another. This study shows that interactions between predator and prey can be extremely complex, involving innate responses, and learned changes in behaviour, which may even occur before birth.

This video from Natalie Beresford (First Year). Why might this cockatoo dance? Is it like a bored tiger or an emprisoned polar bear, or is there something else going on? Why does it do the bow at the end?

Those Final Years who have done the Animal Behaviour course may remember me showing videos of robots behaving like ants. The same Belgian group led by Deneubourg has now turned its attention to cockroaches, as shown by their article in this week’s issue of Science. If you cover a robot with cockroach pheromone, the real roaches follow it. I’m not sure what this is really telling us, apart from indicating the power of the pheromones, or the effect of introducing another object into the cockroaches’ shelter, but the results are impressive.

Definitely a video that will make you laugh! The male red-capped Manakin (Pipra mentalis), a bird found in Costa Rica and Belize (watch out for it if you go there on the Field Course), does a rather cool moonwalk as part of its courtship ritual. It also produces some rather bizarre clicks with its wings. Two YouTube videos show these behaviours:

The smell of a hunter! New study, to appear in Current Biology, shows that elephants apparently remember the smell and look of clothes worn by Maasai hunters, but are not perturbed by the clothes of Kamba agriculturalists who pose no threat.